Cable laying requirements and how to deal with cable laying thermal expansion and contraction

**What Are the Requirements for Cable Laying?** Before laying cables, it is essential to check that the model and specifications meet the required standards. The insulation should be intact, and the cable’s outer surface must be undamaged with no signs of wear or injury. In a three-phase four-wire system, it is not advisable to use a three-core cable along with a single-core cable or a metal-sheathed cable as the neutral conductor. This can lead to imbalances and potential safety issues. Power cables laid in parallel should have the same length to ensure even current distribution and prevent overheating. At the intermediate terminals and near the ends of the cables, sufficient spare lengths should be reserved. For buried cables, these extra lengths should be laid in a wavy pattern to accommodate movement and reduce stress. The spacing between cable supports must follow the design specifications. If no specific requirements are provided, the maximum distance between supports should not exceed 1 meter for horizontal installations, 2 meters for vertical ones, and 0.75 meters for suspended cables. The bending radius of the cable should be at least 10 times the outer diameter of the cable, especially for armored or non-armored multi-core plastic-insulated power cables. When installing cables, they should be pulled from the top of the reel to avoid dragging on brackets or the ground, which could damage the insulation. During installation, cables should not cross each other. They should be neatly arranged, properly secured, and labeled with identification tags. At the bends of buried cables, sturdy stakes should be placed to prevent shifting. When cables enter trenches, tunnels, buildings, or pipes, the entry points should be sealed to prevent moisture or debris from entering. Additionally, any fixtures used for single-core cables should not form a closed magnetic circuit with iron components, as this can cause unwanted heating. **How to Handle Thermal Expansion and Contraction During Cable Installation?** To minimize thermal expansion in large-section cables, split conductors can be used. This not only reduces electrical losses but also lowers the thermo-mechanical forces acting on the cable. The design of cable accessories must account for these forces to avoid damage. There are two main types of cable sheathing: aluminum and aluminum alloy. Aluminum sheathing generally offers better performance compared to aluminum alloy. Therefore, in most cases, aluminum sheathing is the preferred choice for metal-jacketed cables. For directly buried cables, a serpentine layout near the terminal—such as in a substation cable room—can help absorb thermal expansion and reduce the thrust at the end. These sections should be rigidly fixed to prevent displacement that might damage the terminal. When installing large-section cables in conduit systems, bentonite can be used inside the conduits to prevent bending and deformation. At the conduit exit, the cable should be stabilized and fixed to protect the outlet area. Both sides of the cable joint must also be rigidly secured to ensure the safety of the connection. In tunnel installations, cables can be laid in a serpentine pattern to manage thermal expansion and contraction. When installed on slopes, cables must be fixed in place. Additionally, both sides of the joint should be rigidly anchored to protect the integrity of the connection. By following these guidelines, you can ensure safe, efficient, and long-lasting cable installations that comply with industry standards and environmental conditions.

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